<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>作业</title>
	<script type="text/javascript">
	arr = [45,5,78,90];
	//对调arr位置
	function duidiao(x){
		   y=[];
		for(var i=0;i<x.length;i++){
			y[x.length-i-1]=x[i]
		}
		return y;
	}
	y=duidiao(arr);
	alert(y);
	</script>
</head>
<body>
	
</body>
</html>